Within the modern network space, it is frequently required to map data from one transmission protocol (or format) to another. For example, within the Enhanced Data for Global Evolution (EDGE) protocol, data can be mapped to/from any of nine different channel coding schemes, depending on the radio link quality. Each coding scheme provides a respective different data throughput (or rate). Consequently, in order to perform a mapping between any two coding schemes, the data must be rate (or size) adapted. In order to do this, padding data are used to match the size of a data block (of the source coding scheme) to the block size of the destination coding scheme.
For example, FIGS. 1a and 1b respective show representative data frames of two different channel coding schemes. As may be seen in the figures, both frames include a respective header and a data block. The header block is substantially identical in both channel encoding scheme, but in the scheme of FIG. 1b, the data block is larger, thereby reflecting a higher data rate than the frame of FIG. 1a. With this arrangement, mapping data from the frame of FIG. 1a into that of FIG. 1b requires the insertion of padding bits into the data block of FIG. 1b so as to make up for the difference between the data capacity of the higher rate frame (FIG. 1b) and the lower rate frame (FIG. 1a). In the example of FIG. 1b, the padding bits are prepended to the data. However, the padding bits may equally be appended to the data, or they may be split; with some padding bits being prepended to the data and the remainder appended to the data.
Typically, the padding data is provided as either a data fill of binary 1's or 0's. In all cases, conventional forward error correction (FEC) schemes are unaware of padding bits within a data block. The entire data block will be encoded (e.g. using convolutional encoding) and decoded (e.g. using a Viterbi decoder) without reference to the presence or absence of padding bits within the data block. Since the padding bits are known in advance, this leads to redundant encoding and decoding operations, and increases the probability of errored data decoding.
It would be desirable to enhance forward error correction of encoded data containing known padding bits by exploiting the fact that these padding bits are known and not only need not be decoded, but can also be used to improve the probability of decode success of the data.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.